What is the value of B if a = b/c^2 ?

Question

(1) a*c^2 = 50
(2) c^2 = 10 and a^2 = 25

Kudos for a correct  solution .

noTh1ng · Answer

a = b / c^2
a * c^2 = b

1.: is exactly that statement. a*c^2= 50, so b = 50. Sufficient

2.: Insert values for a and c^2 and the result will be b = 50 as well. Sufficient.

Answer: D

suket25 · Answer

Its A.

Statement 2: a=+-5;
b=50 Or -5

Ankur9 · Answer

To Find: b= ac^2
1. ac^2 = 50 
sufficient

2. c^2 = 10
a^2 = 25 --> a=5
thus ac^2=5*10=50
sufficient

D

King407 · Answer

a=\frac{b}{c^2} => a*c^2 = b

A)  a*c^2 = 50 =b .  Sufficient

B)  a^2 = 25 => a=+5 or -5 => b= 50 or -50 .  Insufficient

Hence, Answer is A

EMPOWERgmatRichC · Answer

Hi All,

The GMAT will test you several times on the concept of 'squared terms.' It's important to remember that when you start off with a squared term set equal to a positive number that there are TWO solutions - one positive and one negative.

eg. X^2 = 16

X could be 4 or -4 and you are responsible to consider both possibilities (unless the given prompt 'restricts' the math in some way - for example, by stating that X is negative).

This specific issue impacts this question, so you have to be thorough enough in your work to spot it and properly deal with it.

GMAT assassins aren't born, they're made,
Rich

funkyleaf · Answer

The question asks us if it is possible to calculate a single definite value of B.

1) rearranging the equation given in the stem algebraically we can see that a*c^2=b therefore 50=b giving us a single definite answer for the value of b, Sufficient. Eliminate choices B, C, E.

2) Here we see that a^2 = 25, without further information we can only say that a=5 or a=-5. Plugging these values in along with c^2 = 10 we get b=50 or b=-50 not allowing for a single definitive answer for what the value of b is without further information. Eliminate choice D.

Select answer A.

Bunuel · Answer

KAPLAN OFFICIAL SOLUTION:

First, you can multiply both sides of the equation in the question stem by c^2 to make it clear that ac^2 = b. Then, look for values a, c and ac^2.

Statement (1) is exactly what is needed – it gives you a precise value for ac^2. Statement (1) is sufficient, so eliminate answer choices C and E.

Statement (2) alone, however, leads to two possible values for b, because you’d have to substitute the square roots of 25 for a, and those square roots are BOTH positive AND negative 5 (remember this! The GMAT likes to test you on your knowledge that both a positive and negative number can be squared to produce a positive result.) Therefore, Statement (2) is insufficient because it does not give you one single value. Eliminate answer choices B and D.

The correct answer is A.

kelvind13 · Answer

your assumption of statement 2 is wrong. a could either be 5 or -5. making statement 2 insufficient

D3N0 · Answer

First of all i think its 'b' not 'B'

for that b=a*c^2
Ans: A

1) a*c^2=50; Sufficient
2) c^2=10, a^2=25 so a can be +5,-5 so b=50 0r -50 not Sufficient

Ans: A

Ved22 · Answer

Hello Champ,

B can not be sufficient. Since its b2 = 25 and then b can take value either +5 or -5. No single value can be determined. So only Statement A is sufficient to answer

What is the value of B if a = b/c^2 ?

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GMAT Data Sufficiency (DS) Questions

What is the value of B if a = b/c^2 ?

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